Water-holding materials such as organic cross-linked polymers have been used for many years to absorb and hold moisture. They have been designed and used to improve the capability of soils and other growing media by retaining water and plant nutrients. By absorbing water, they provide a readily available source of water that is essential for proper plant growth. These polymers serve as a reservoir of water that is available for plants, seeds, and/or soil as needed. These polymers are typically used for mixing into growing media prior to seeding, sodding or small container planting. Also, they can be used for root dipping. These polymers are typically potassium or sodium based polymers. Claimed benefits pertaining to the additional moisture available include: less time spent watering, better irrigation control, increased shelf life of plants, better survival rates, provides aeration in soil, reduced transplant shock, and help reduce media volume, all of which relate to the benefits associated with the polymers ability to serve as a water reservoir (absorbing and releasing) for the plants, seeds, and/or soil direct use.
Germination begins when water is absorbed (imbibed) by the seed. As reported in Turfgrass: Science and Culture by James B. Beard (1973 by Prentice-Hall, Inc):
Environmental conditions necessary for rapid, complete germination of turfgrass seeds include (a) an adequate water supply, (b) favorable temperatures, (c) an adequate oxygen supply, and (d) exposure to light. Water has a vital role since water absorption by imbibition and osmosis is the first physiological step in seed germination. Water functions in softening and swelling of the seed, which facilitates the entrance of oxygen and dilutes the protoplasm. Normal digestion, respiration, and assimilation processes are activated when the protoplasm becomes sufficiently moist. Soluble carbohydrates are transferred from the endosperm to the embryo.
A number of practices can be employed during the establishment phase to ensure the rapid development of a dense, tight sod. Proper irrigation is a key factor in successful turfgrass establishment. One of the most critical practices during both the germination and establishment phases is irrigation. The soil zone where seed germination and seedling growth activity occur should be maintained in a moist condition at all times.
Failure to maintain an adequate moisture level is one of the major causes of poor turfgrass establishment. Young turfgrass seedlings have an extremely short root system that depends on a readily available moisture supply at the soil surface. The surface of un-mulched soils can dry out very rapidly during periods of high light intensity and high temperatures. The soil surface should be maintained in a moist condition for at least three weeks following planting.
When it comes to germination and establishment, plant available moisture is the limiting factor as it controls turfgrass growth and aesthetic appearance more than any other environmental factors.
Most people simply do not know when to start and stop watering newly planted seeds to assist in the germination and establishment process. Currently, gauges exist to measure amounts of rainfalls and timers exist to activate/deactivate irrigation systems at specified times. Further technology exists that automate the watering process at research facilities based on electronic indicators. None of these provide a simple visual indicator that is available to the general public to serve as a when-to-water guide.